In a storage device using a NAND flash memory (NAND memory), error correction (Error Check and Correct) is performed, and a data which is to be written in the NAND memory is encoded to be written in each page of the NAND memory. As error correction process, there is an inner-page ECC (Error Check and Correct) where one code word is configured with symbols in the same page and an inter-page ECC where one code word is configured with symbol in different pages. In a case where random error is beyond correction capability (error-correctable number of symbols) of the inner-page ECC, or in a case where burst error, that is, data loss in unit of a page occurs due to circuit disorder, the error can be corrected by using the inter-page ECC.